Robotic vehicle deck adjustment

ABSTRACT

A robotic vehicle is disclosed, which is characterized by high mobility, adaptability, and the capability of being remotely controlled in hazardous environments. The robotic vehicle includes a chassis having front and rear ends and supported on right and left driven tracks. Right and left elongated flippers are disposed on corresponding sides of the chassis and operable to pivot. A linkage connects a payload deck, configured to support a removable functional payload, to the chassis. The linkage has a first end rotatably connected to the chassis at a first pivot, and a second end rotatably connected to the deck at a second pivot. Both of the first and second pivots include independently controllable pivot drivers operable to rotatably position their corresponding pivots to control both fore-aft position and pitch orientation of the payload deck with respect to the chassis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. patent application is a continuation of U.S. application Ser.No. 11/762,315, filed Jun. 13, 2007 which claims priority to a U.S.provisional patent application 60/828,606 filed on Oct. 10, 2006, theentire contents of which are hereby incorporated by reference.

STATEMENT AS TO FEDERALLY SPONSORED RESEARCH

This invention was in part with Government support under contractN41756-06-C-5512 awarded by the Technical Support Working Group of theDepartment of Defense. The Government may have certain rights in theinvention.

TECHNICAL FIELD

This disclosure relates to robotic vehicles.

BACKGROUND

A new generation of robotic systems and tools is required to meet theincreasing terrorist threat in the US and abroad. The lack ofadaptability and limited capability of existing remote controlledsystems available to Hazardous/First Response/Explosive OrdnanceDisposal (EOD) teams has frustrated many teams worldwide. The unique andoften dangerous tasks associated with the first responder missionrequire personnel to make quick decisions and often adapt their tools inthe field to combat a variety of threats. The tools must be readilyavailable, robust, and yet still provide surgical precision whenrequired.

SUMMARY

According to one aspect of the disclosure, a robotic vehicle includes achassis having front and rear ends and supported on right and leftdriven tracks, each track trained about a corresponding front wheelrotatable about a front wheel axis. Right and left elongated flippersare disposed on corresponding sides of the chassis and operable to pivotabout the front wheel axis of the chassis, each flipper having a driventrack about its perimeter. A linkage connects a payload deck assembly,configured to support a functional, securely mounted and integratedpayload (in some cases, modular payloads, unconnected payloads and/orfunctional payload), to the chassis. The linkage has a first endrotatably connected to the chassis at a first pivot, and a second endrotatably connected to the deck at a second pivot. Both of the first andsecond pivots include independently controllable pivot drivers operableto rotatably position their corresponding pivots to control bothfore-aft position (as well as vertical position, the pivots beinginterconnected by a linkage that makes a swept motion) and pitchorientation of the payload deck assembly with respect to the chassis. Inone example, the first pivot is rotatable through an angle of at least180 degrees. The first pivot is not necessarily limited by a range ofmotion of the pivot, but rather by those positions in which the linkage,deck assembly, or payload interfere with part of the robot such as thechassis or with the ground—which may depend on the character of theground and pose of the robot. Accordingly, in another implementation,the sweep of the linkage is limited by the chassis of the robot, whichis configured as small tube element connecting chassis arms. The deckassembly and linkage may sweep between the chassis arms and between theflippers in either direction, and may sweep past a horizontal linedefined by one chassis track wheel and bogey, in either direction foreor aft of the pivot. In another implementation, the sweep is limited to74 degrees to improve stability and shock resistance on open ground. Ineach case, the payload deck assembly, with or without payload(s), may betilted to move the center of gravity of the robot further in a desireddirection. The linkage may comprise two parallel links spaced apartlaterally.

The independently controllable pivot drivers provide both fore-aftposition (and a wide sweep range) and pitch orientation of the payloaddeck assembly with respect to the chassis to selectively displace acenter of gravity of the payload deck assembly both forward and rearwardof a center of gravity of the chassis. This provides enhanced mobilityto negotiate obstacles. Hereinafter, center of gravity or center of massmay be abbreviated “CG.”

Rotation of the linkage about its first and second pivots enablesselective positioning of a center of gravity or center of mass of thepayload deck assembly both fore and aft the front wheel axis as well asboth fore and aft of a center of gravity of the chassis. In oneimplementation, the first pivot of the linkage is located above andforward of the front wheel axis and swings the linkage for displacingthe center of gravity of the payload deck assembly to a desiredlocation. Furthermore, when the first end of the linkage is rotatablyconnected near the front of the chassis, the payload deck assembly isdisplaceable to an aftmost position in which the payload deck assemblyis located within a footprint of the chassis.

In one example, the payload deck assembly includes connection points forboth a functional payload power link and a functional payloadcommunication link, which may comprise an Ethernet link. In oneimplementation, the functional payload communication link is a packetswitched network connectable to a distribution switch or router.

The payload deck assembly includes an electronics bin (also “CG tub”)which holds most of the electronics of the robot (as well as the uppermotor(s) for tilting the paylaod deck assembly, but excepting motorcontrol and drivers for the drive motors, which is housed in thechassis), and supports a dockable battery unit slid into the bottom ofthe electronics bin as well as a accepting a modular payload deck, whichdefines threaded holes to accept functional payloads and includesmultiple functional payload connection pads positioned to accommodateselective connection of multiple functional payload units to the payloaddeck. Each connection pad includes connection points for both functionalpayload power and functional payload communication (as well assufficient hard points nearby for such payloads to be secured to thedeck with sufficient fasteners to reliably secure the mass of thepayload through tilting operations of the deck). The payload deck canaccept as a payload unit a removable radio receiver unit (which cancommunicate with a remote controller unit) operably connected to a drivesystem of the chassis. A battery unit is also removable secured to thebottom of the deck, so as to place the significant weight of batteriesas low as possible in the mass that is used for shifting the center ofgravity of the vehicle. In one example, the payload deck constitutesbetween about 30 and 50 percent of a total weight of the vehicle. Thepayload deck may also accept an Ethernet camera as a payload unit.

In one implementation, the payload deck further accepts as payload unitsremovable sensor units. The sensor may be, for example, infrared,chemical, toxic, light, noise, and weapons detection.

The left and right flippers comprise elongated members, wherein flippertracks are trained about corresponding rear wheels independentlyrotatable about the front wheel axis.

The robotic vehicle can climb a step by using the independentlycontrollable pivot drivers to control both sweep and pitch orientationof the payload deck assembly with respect to the chassis to selectivelydisplace the center of gravity of the payload deck assembly the bothforward and rearward of the center of gravity of the chassis. Therobotic vehicle may initiates a step climb by pivoting the first andsecond flippers upward to engage the edge of the step. Differentobstacles can be accommodated by different strategies that use the fullrange of the sweepable and tiltable CG of the entire payload deckassembly, or of the payload deck assembly when combined with a payload.An advantage of the disclosed system is that the addition of payloadweight on the payload deck assembly increases the flexibility andmobility of the robot with respect to surmounting obstacles of variousshapes. The robotic vehicle also positions the center of gravity of thepayload deck assembly above the front end of the chassis. Next, therobotic vehicle pivots the first and second flippers downward on theedge of the step to engage the top of the step and drives forward. Therobotic vehicle continues to displace the center of gravity of thepayload deck assembly beyond the front of the chassis by rotating boththe first and second pivots. As shown in FIG. 14, tilting the deckassembly further advances the center of gravity of the entire vehicle.Finally, the robotic vehicle drives forward to pull the chassis over theedge of the step.

In another aspect of the disclosure, a skid steered robot includes achassis supporting a skid steered drive and a set of driven flippers,each flipper being pivotable about a first pivot axis common with adrive axis of the chassis. A linkage substantially at the leading end ofthe chassis is pivotable about a second pivot axis. A deck assembly ispivotable about a third pivot axis substantially at a distal end of thelinkage. The deck assembly includes a power supply, a packet networkconnection, a modular deck support structure; and a modular deck. Themodular deck includes a deck mount which fits the modular deck supportstructure and at least two externally available common connectors. Atleast one of the deck assembly or modular deck includes a power supplyswitching circuit that switches available power from the power supplybetween the at least two common connectors, and a network switch thatswitches packet network traffic between the at least two commonconnectors.

In another aspect of the disclosure, a skid steered robot includes a setof driven flippers, each flipper being pivotable about a first pivotaxis common with a drive axis of the chassis. A deck assembly, disposedabove the chassis, includes a power supply, a packet network connection,a modular deck support structure, a deck wiring harness connectorincluding packet network cabling and power cabling, and a modular deck.The modular deck includes a deck mount which fits the modular decksupport structure, at least two externally available common connectors,a power supply switching circuit that switches available power from thepower supply between at least two common connectors, a network switchthat switches packet network traffic between the at least two commonconnectors, and a deck wiring harness that connects to the deck wiringharness connector and carries power and network to and from the modulardeck.

In another aspect of the disclosure, a modular deck for a roboticvehicle includes a base configured to be secured to the vehicle, whereinthe base receives both a power link and a communication link from therobotic vehicle. A platform configured to support a removable functionalpayload is secured to the base and has at least one connection point forboth a functional payload power link and a functional payloadcommunication link. The connection point is linked to both the basepower link and the base communication link.

The details of one or more implementations of the invention are setforth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages of the invention will be apparent fromthe description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a robotic vehicle.

FIG. 2 is an exploded view of the robotic vehicle.

FIG. 3 is a front view of the robotic vehicle.

FIG. 4 is a back view of the robotic vehicle.

FIG. 5 is a top view of the robotic vehicle.

FIG. 6 is a bottom view of the robotic vehicle.

FIG. 7 is an exploded perspective view of the robotic vehicle.

FIG. 8 is a side view of the robotic vehicle.

FIG. 9 is an side view of the robotic vehicle.

FIG. 10 is a perspective view of a payload deck for a robotic vehicle.

FIG. 11 is a perspective view of a payload deck for a robotic vehicle.

FIG. 12 is a perspective view of a payload deck for a robotic vehicle.

FIG. 13 is a perspective view of the robotic vehicle with a manipulatorarm.

FIGS. 14-17 are side views of a robotic vehicle climbing.

FIGS. 18-21 are side views of a robotic vehicle climbing.

FIG. 22 is a side view of a robotic vehicle climbing stairs.

FIG. 23 is a front view of a robotic vehicle traversing an incline.

FIG. 24 is a perspective view of a robotic vehicle in a neutral posture.

FIG. 25 is a perspective view of a robotic vehicle in a standingposture.

FIG. 26 is a perspective view of a robotic vehicle in a kneelingposture.

FIG. 27 is a perspective view of a robotic vehicle in a kneelingposture.

FIG. 28 is a side view of a robotic vehicle.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring to FIG. 1, a robotic vehicle 10, in one implementation, is aremotely operated vehicle that enables the performance of manpowerintensive or high-risk functions (i.e., explosive ordnance disposal;urban intelligence, surveillance, and reconnaissance (ISR) missions;minefield and obstacle reduction; chemical/toxic industrial chemicals(TIC)/toxic industrial materials (TIM); etc.) without exposing operatorsdirectly to a hazard. These functions often require the robotic vehicle10 to drive quickly out to a location, perform a task, and either returnquickly or tow something back. The robotic vehicle 10 is operable from astationary position, on the move, and in various environments andconditions.

Referring to FIGS. 1-6, a robotic vehicle 10 includes a chassis 20 thatis supported on right and left drive track assemblies, 30 and 40respectively, having driven tracks, 34 and 44 respectively. Each driventrack 34, 44, is trained about a corresponding front wheel, 32 and 42respectively, which rotates about front wheel axis 15. Right and leftflippers 50 and 60 are disposed on corresponding sides of the chassis 20and are operable to pivot about the front wheel axis 15 of the chassis20. Each flipper 50, 60 has a driven track, 54 and 64 respectively,about its perimeter that is trained about a corresponding rear wheel, 52and 62 respectively, which rotates about the front wheel axis 15.

Referring to FIG. 7, in one implementation, the robotic vehicle 10includes right and left motor drivers, 36 and 46, driving correspondingdrive tracks, 34 and 44, and flipper tracks, 54 and 64, which aresupported between their front and rear ends by bogie wheels 28. Aflipper actuator module 55 is supported by the chassis 20 and isoperable to rotate the flippers, 50 and 60. In one example, the flippers50, 60 are actuated in unison. In other examples, the flippers 50, 60are actuated independently by right and left flipper actuators 55.

Referring to FIG. 8, a linkage 70 connects the payload deck assembly 80to the chassis 20. The linkage 70 has a first end 70A rotatablyconnected to the chassis 20 at a first pivot 71, and a second end 70Brotatably connected to the payload deck 80 at a second pivot 73. Both ofthe first and second pivots, 71 and 73 respectively, include respectiveindependently controllable pivot drivers, 72 and 74, operable torotatably position their corresponding pivots to control both fore-aftposition and pitch orientation of the payload deck assembly 80 withrespect to the chassis 20. As shown in FIGS. 1-2, the linkage 70 maycomprise two parallel links spaced apart laterally.

Referring to FIG. 9, the first end 70A of the linkage 70 is rotatablyconnected near the front of the chassis 20 such that the payload deckassembly 80 is displaceable to an aftmost position in which the payloaddeck assembly 80 is located within a footprint of the chassis 20.Furthermore, as shown in FIGS. 1-2, the first pivot 71 of the linkage 70is located above and forward of the front wheel axis 15. The first pivot71 is rotatable through an angle of at least 180 degrees (optionally, 74degrees), in one example. Rotation of the linkage 70 about its first andsecond pivots, 71 and 73 respectively, enables selective positioning ofcenter of gravity 410 of payload deck assembly 80 both fore and aftfront wheel axis 15 as well as both fore and aft a center of gravity 400of the chassis 20. In another example, the independently controllablepivot drivers 72, 74 provide both fore-aft position (as part of sweep)and pitch orientation of the payload deck assembly 80 with respect tothe chassis 20 to selectively displace the center of gravity 410 of thepayload deck assembly 80 both forward and rearward of the center ofgravity 400 of the chassis 20, displacing a center of gravity 450 of theentire robot 10.

The robotic vehicle 10 is electrically powered (e.g. a bank of ninestandard military BB-2590 replaceable and rechargeable lithium-ionbatteries). Referring to FIGS. 2-3, the payload deck assembly 80,specifically the electronics tub 90, accommodates a slidable, removablebattery unit 92. Skid pad 94, as shown in FIG. 6, may be secured to thebottom of the battery unit 92 to protect the battery 92 and aidmanageability. The payload deck assembly 80 may carry an additionalbattery supply on one of the selectable connection pads 810, increasingthe available power capacity (e.g. an additional bank of nine batteriesmay be carried on payload deck).

Referring again to FIGS. 2-6, a payload deck assembly 80, including anelectronics bin 90 and payload deck 806 (D1, D2, D3 in other drawingsherein), is configured to support a removable functional payload 500.FIGS. 3-4 illustrate the robotic vehicle 10 with the payload deckassembly 80 including front and rear functional payload powerconnectors, 200 and 210, and a user interface panel 220. FIG. 2illustrates one example where the payload deck assembly 80 includesfront and rear sensor pods, 240 and 250 respectively. In someimplementations, the sensor pods 240, 250 provide infrared, chemical,toxic, light, noise, and weapons detection, as well as other types ofsensors and detection systems. A primary driving sensor may be housed ina separate audio/camera sensor module mounted to the payload deckassembly 80 that contains at least one visible spectrum camera. Audiodetection and generation is realized using an audio/camera sensor modulemounted to the payload deck assembly 80, in one example.

In some implementations, robotic vehicle 10 tows a trailer connected torear payload connector 290, as shown in FIG. 5. Exemplary payloads forthe trailer include a small generator, which significantly extends bothrange and mission duration of robotic vehicle, field equipment, andadditional functional payload units 500 attachable to the payload deckassembly 80.

The payload deck assembly 80 accepts the mounting of one or morefunctional payload modules 500 that may include robotic arms, chemical,biological and radiation detectors, and a sample container. The roboticvehicle 10 automatically detects the presence and type of an installedfunctional payload 500 upon start-up. Referring to FIG. 5, the payloaddeck 806 defines threaded holes 808 to accept a functional payload 500.FIG. 5 also illustrates one or more functional payload connection pads810 positioned on the payload deck assembly 80 to accommodate selectiveconnection of multiple functional payload units 500. Each functionalpayload connection pad 810 delivers power, ground and communications toa functional payload unit 500. For example, robotic vehicle 10 mayprovide up to 300 W (threshold), 500 W (goal) of power to a payload 500at 42V, up to 18 A. The communication link may include Ethernet linkcommunications. In one example, payload deck assembly 80 constitutesbetween about 30 and 70 percent of the vehicle's total weight. Thepayload deck assembly 80 further includes a removable controller unit350 operably connected to a drive system (e.g. the motor drivers 36, 46)of the chassis 20. The robotic vehicle 10 communicates with an operatorcontrol unit (OCU) through optional communication functional payloadmodule(s) 500. The robotic vehicle 10 is capable of accepting andcommunicating with a radio functional payload module 500.

Referring to FIGS. 10-12, modular decks D1, D2, D3 are removable payloaddecks 806 modularly secured to the electronics bin 90 to form thepayload deck assembly 80. The modular decks D1, D2, D3 maintainconnectivity to functional payloads 500 located on the decks D1, D2, D3while allowing interchangeability with a payload deck assembly base 805.The modular decks D1, D2, D3 receive power and communication from a deckconnector 802 attached by a wiring harness 804. FIG. 17 depicts adevelopment deck Dl including sparsely spaced connector pads 806. FIG.18 depicts a mule deck D2 including netting 808 for carrying loads andat least one connector pad 806. FIG. 19 depicts a manipulator deck D3including an integral bracing 810 for a large manipulator arm. Theintegral bracing 810 housing at least one connector pad 806. Theconnectors pads 806 available on the decks D1, D2, D3 each carry 42V, upto 18 A power; ground; and Ethernet, for example. FET switches connectedto each connector pad 806 are overload protected and are controlled by adigital signal processor (DSP) on the deck to distribute power. The DSPis controlled via a controller area network (CAN) bus, a knownindustrial and automotive control bus.

FIG. 13 illustrates a robotic arm module 600 as a functional payload 500attached to the payload deck assembly 80. The robotic arm module 600provides full hemispherical reach (or more, limited only byinterference; or less, limited by other needs of the robot 10) aroundthe robotic vehicle 10. The robotic arm module 600 provides liftingcapacity and an additional means for shifting the robotic vehicle'scenter of gravity 450 forward, e.g. when ascending steep inclines, andrearward, e.g. for additional traction.

The robotic vehicle 10 may sense elements of balance through the linkage70 (e.g., via motor load(s), strain gauges, and piezoelectric sensors),allowing an operator or autonomous dynamic balancing routines to controlthe center of gravity 410 of the payload deck assembly 80 and the centerof gravity 430 of the linkage 70 for enhanced mobility, such as to avoidtip over while traversing difficult terrain.

FIGS. 14-17 illustrate the robotic vehicle 10 climbing a step by usingthe independently controllable pivot drivers 72 and 74 to control bothfore-aft position and pitch orientation of the payload deck assembly 80with respect to the chassis 20 to selectively displace the center ofgravity 410 of the payload deck assembly 80 both forward and rearward ofthe center of gravity 400 of the chassis 20. Referring to FIG. 14, instep 51, the robotic vehicle 10 initiates step climbing by pivoting thefirst and second flippers 50 and 60, respectively, upward to engage theedge 902 of the step 900. The robotic vehicle 10 also positions thecenter of gravity 410 of the payload deck assembly 80 above the frontend of chassis 20. Next, as shown in FIGS. 15-16, in steps S2 and S3,the robotic vehicle 10 pivots the first and second flippers 50 and 60downward on the edge 902 of the step 900 to engage the top 904 of thestep and drives forward. In FIG. 15, illustrating step S2, the payloaddeck assembly 80 is further tilted to advance the center of gravity 450of the robot 10 (permitting higher obstacles to be climbed). In step S3,the robotic vehicle 10 continues to displace the center of gravity 410of the payload deck assembly 80 beyond the front of the chassis 20, asshown in FIG. 16, by rotating both the first and second pivots, 71 and73 respectively. Finally, in step S4, as shown in FIG. 17, the roboticvehicle 10 drives forward to pull the chassis 20 over the edge 902 ofthe step 900. FIGS. 18-21 illustrates the robotic vehicle 10 initiatingand completing steps S1-S4 for obstacle climbing with a functionalpayload 500 secured to the payload deck assembly 80.

In some implementations, the robotic vehicle 10 is configured tonegotiate obstacles, curbs and steps having a height of about 0.3 m (12inches), and across a horizontal gap of about 0.61 m (24 inches). Therobotic vehicle 10 has side-to-side horizontal dimensions smaller thanstandard exterior doorways (e.g. 32 inches) and interior doors (e.g. 30inches). Referring to FIGS. 22-23, the robotic vehicle 10 is configuredas to ascend and descend a flight of stairs having up to a climb angle,β, of about 37 degrees, as well as climb and descend an inclined slope,including stopping and starting, on a hard dry surface slope angle, β,of about 50 degrees. Similarly, the robotic vehicle 10 is physicallyconfigured as described herein to climb and descend, including stoppingand starting, an inclined grass covered slope having an angle, β, ofabout 35 degree grade. The robotic vehicle 10 is configured to laterallytraverse, including stopping and starting, on a grass slope angle, φ, ofabout 30 degrees. Furthermore, the robotic vehicle 10 is configured tomaneuver in standing water (fresh/sewage) having a depth of about 0.3 m(12 inches) and maintain a speed of about 20 kph (12 mph) on a pavedsurface, and about 8 kph (5 mph) through sand and mud.

The robotic vehicle 10 supports assisted teleoperation behavior, whichprevents the operator from hitting obstacles while using on boardobstacle detection/obstacle avoidance (ODOA) sensors and responsive ODOAbehaviors (turn away; turn around; stop before obstacle). The roboticvehicle 10 assumes a stair climbing pose, as illustrated in FIG. 13, ora descending preparation pose (similar to the pose shown in FIG. 13, butwith the flippers 50, 60 pointing downward) when a stair climbing orstair descending assist behavior is activated, respectively. The roboticvehicle 10 stair climbing behaviors can be configured to control (tilt)the flippers 50, 60 and control the position of the center of gravityshifter 70 as the robot 10 negotiates stairs. A stair climbing assistbehavior keeps the robotic vehicle 10 on a straight path up stairs and,in one example, may maintain a roll angle of about zero degrees.

The robotic vehicle's 10 control software provides autonomouscapabilities that include debris field mapping, obstacle avoidance, andGPS waypoint navigation. The robotic vehicle 10 can determine positionvia a global positioning system (GPS) receiver, housed in a separatesensor module 500.

The robotic vehicle 10 is fully operational after exposure to atemperature range of about −40° C. to about 71° C. (−40° F. to 160° F.)in a non-operating mode and is fully operational in a temperature rangeof about −32° C. to about 60° C. (−26° F. to 140° F.). The roboticvehicle operates during and after exposure to relative humidity up toabout 80 percent, in varied weather conditions. The robotic vehicle 10also operates during and after exposure to blowing sand and/or rain,freezing rain/ice, and in snowfall up to about 0.1 m (4 inches) indepth.

Referring to FIGS. 24-28, the robotic vehicle 10 may exhibit a varietyof postures or poses to perform tasks and negotiate obstacles. Thelinkage 70 together with the deck assembly 80, chassis 20, and flippers50, 60 all move to attain a number of standing postures. FIG. 24 depictsrobotic vehicle 10 in a neutral posture. FIG. 25 depicts the roboticvehicle 10 in one standing posture wherein the distal end of flippers 50and 60 approaches the leading end of the chassis 20 to form an acuteangle between the flippers 50 and 60 and the chassis 20. The linkage 70is entirely above a common axis 15 of the flippers 50 and 60 and thechassis 20. In one example, the deck assembly 80 tilts independentlywith respect to the robotic vehicle 10. The acute angle achieved betweenthe flippers 50 and 60 and the chassis 20 varies the standing positionswithout changing the orientation of the deck assembly 80 with respect tothe ground. In some examples, the linkage 70 is positionable at leastparallel to an imaginary line between the distal and pivot ends offlippers 50 and 60. In additional examples, the second end 70B of thelinkage 70 is positionable below an imaginary line between the distaland pivot ends of flippers 50 and 60. In another implementation, thelinkage 70 together with the deck assembly 80, chassis 20, and flippers50 and 60 can move to attain a first kneeling position, as shown in FIG.26, and a second kneeling position, as shown in FIG. 27.

FIG. 28 illustrates an implementation of centers of gravity of a roboticvehicle 1000 and distances between them. The locations of the centers ofgravity within the chassis 20, deck 80, linkage 70, and flippers 50 and60 and with respect to each other individually may be varied to attain anumber of advantages in terms of maneuverability and the ability toperform certain tasks.

There are several advantages to the present “two-bar” linkage 70 (havingindependent, powered pivots 71, 73 at the deck assembly end 70B and thechassis end 70A of the linkage 70) with respect to other structures forshifting a center of gravity.

For example, a robot equipped with a “two-bar” linkage 70 can scalehigher obstacles relative to a robot without such a linkage. In order todo so, the deck assembly 80 is tilted and/or pivoted further forward,moving the overall center of gravity 450 higher and farther forward. Arobot equipped with the two-bar linkage 70 can scale higher obstacleswhen bearing a payload 500 on top of the deck assembly 80 than without apayload 500. A high, heavy payload 500 can be tipped with the two-barlinkage 70 to provide a more pronounced shift of the center of gravity450 forward than an empty deck assembly 80. The two bar linkage 70 mayraise the deck assembly 80 and an attached a sensor pod module 500higher in a standing position, as shown in FIG. 25, even with a leveldeck, because the linkage 70 is connected at one point 73 at the top ofthe range and also at one point 71 at the bottom of the range. This isvaluable because the linkage 70 may place a sensor such as a camera,perception sensor (e.g., laser scanner) or payload sensors 500relatively higher. Other linkage systems may require connection at morethan one point, which may limit the height and/or may also tilt the deckassembly 80 at the highest position while in the standing position.

A two bar linkage 70 has a theoretical pivot range, limited only byinterference with other parts of the robot, of greater than 180 degrees.If positioned concentrically with the flipper-chassis joining axis 15,the linkage rotation range could be 360 degrees. Other constraintsdesigned herein and other advantages obtainable in other positions canchange this. For example, if the first pivot 71 of the linkage 70 ispositioned above and forward of the common chassis-flipper axis 15(e.g., about 20 mm forward and about 70 mm above), it is possible tohave a unitary structure for the chassis 20 (casting).

A straight shaft may join both flippers 50,60 directly, allowing thebottom pivoting actuator 72 to be placed off center with the flipperactuator 55. Additional pivot range past 180 degrees may be obtained, aswith additional standing height, by increasing the distance between thefirst pivot 71 and the common chassis-flipper axis 15.

Other systems may have a range of considerably less than 180 degrees,for example if the parts of such systems are limited in a pivoting ormovement range by interference among the system members. Still further,a two bar linkage has a longer effective forward extending range, sincethe linkage 70 is substantially stowable to the chassis 20. The distancebetween more than one chassis connections of the other systems mayshorten the effective forward extending range. As one additionaladvantage, a deck-side actuator 74 of the two-bar linkage 70 can be usedto “nod” (auxiliary scan) a scanning (main scanning) sensor such as a 2DLADAR or LIDAR to give a 3D depth map.

Other robotic vehicle details and features combinable with thosedescribed herein may be found in a U.S. Provisioned filed Oct. 6, 2006,entitled “MANEUVERING ROBOTIC VEHICLES” and assigned Ser. No.60/828,611, the entire contents of which are hereby incorporated byreference.

A number of implementations of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, flippers of varied length and payload decks with other means offunctional payload attachment, such as snap-on, clamps, and magnets.Accordingly, other implementations are within the scope of the followingclaims.

1. A method performed by a robotic vehicle for climbing a step, themethod comprising, in order substantially as recited: approaching thestep; pivoting tracked flippers upward to engage an edge of the step;pivoting the tracked flippers downward to engage a top of the step;driving the vehicle forward on driven tracks different from the trackedflippers; rotating each of first and second pivots at opposite ends of alinkage that connects a payload deck to a chassis of the robotic vehicleto position the center of gravity of the payload deck and any removablepayload thereon beyond the front end of the chassis and beyond the edgeof the step; moving the center of gravity of the payload deck and anyremovable payload thereon further beyond the front end of the chassis,thereby causing the deck to tilt with respect to the chassis; anddriving the vehicle forward to pull the chassis over the edge of thestep.
 2. The method of claim 1, wherein both of the first and secondpivots include independently controllable pivot drivers operable torotatably position their corresponding pivots to control both fore-aftposition and pitch orientation of the payload deck with respect to thechassis.
 3. The method of claim 1, wherein a robotic arm module issecured to the payload deck.
 4. The method of claim 3, wherein rotatingthe first and second pivots to position the center of gravity of thepayload deck and any removable payload thereon beyond the edge of thestep includes extending the robotic arm module to shift the center ofgravity of the payload deck further beyond the edge of the step.
 5. Themethod of claim 1, wherein a removable payload is secured to the payloaddeck, and the removable payload provides additional weight to thepayload deck, and wherein rotating the first and second pivots toposition the center of gravity of the payload deck beyond the edge ofthe step provides a more pronounced shift of the center of gravity ofthe payload deck than would be provided with an empty payload deck. 6.The method of claim 1, wherein rotating the first and second pivots toposition the center of gravity of the payload deck beyond the edge ofthe step includes sensing elements of balance through the linkage. 7.The method of claim 6, wherein sensing elements of balance through thelinkage is accomplished using one or more of: one or more motor loads,one or more strain gauges, and one or more piezoelectric sensors.
 8. Themethod of claim 1, wherein the robotic vehicle further comprises acontroller disposed on the payload deck and connected to the chassis bythe linkage, and operable connected to motor drivers of the chassis todrive the right and left tracks.
 9. The method of claim 8, wherein thecontroller unit is removable from the payload deck.
 10. The method ofclaim 1, wherein the payload deck further comprises a removable batteryunit.
 11. The method of claim 1, rotating the first and second pivots toposition the center of gravity of the payload deck beyond the edge ofthe step includes rotating the first pivot through an angle of at least180 degrees.
 12. The method of claim 1, wherein the payload deck,including a removable payload, constitutes between about 30 and 50percent of a total weight of the vehicle.
 13. The method of claim 1,wherein the payload deck includes multiple payload connection padspositioned to accommodate selective connection of multiple payload unitsto the payload deck, and each connection pad includes connection pointsfor both payload power and payload communication.
 14. The method ofclaim 13, wherein a removable payload is secured to the payload deck tomake a connection between the removable payload and the payload deck viathe connection pads.
 15. The method of claim 1, wherein the first pivotof the linkage is located above and forward of the front wheel axis.